Circuit boards, which are used as memories, processors, etc. included in information processing equipment such as personal computers, servers, routers, and storages, informational on-board terminals, and information home appliances such as televisions and cameras, play an extremely important role as functional circuits or boards connecting functional modules.
However, in such circuit boards, ion migration that occurs due to moisture from water vapor and the like has become a problem in recent years. When ion migration occurs, a metal used as wiring moves on a board, and may ultimately destroy the circuit board.
Therefore, for example, Patent Document 1 (JP Laid-open Patent Publication No. 2003-124580) discloses, in order to provide water-vapor barrier property, a laminated body obtained by laminating a film formed from a thermoplastic resin that shows optical anisotropy when being melted on a circuit surface of a flexible printed wiring board through a pressure-sensitive adhesive layer and/or an adhesive layer.
In addition, Patent Document 2 (JP Laid-open Patent Publication No. 2007-19338) discloses an electronic circuit board comprising a liquid crystal polymer sheet, the liquid crystal polymer sheet having a surface on which a short-wavelength ultraviolet ray is irradiated, and being thermocompressively bonded on circuit surface(s) formed on one surface or both surfaces of a liquid crystal polymer sheet in a state that the circuit surface(s) and the irradiation surface are in contact with each other.
In such laminated body as well as electronic circuit board, it is possible to provide water resistance to a circuit board by covering circuit surface(s) with a liquid crystal polymer sheet.